ANATOMICAL ANALYSIS OF NEURONAL CIRCUITS

我们以前已经确定了一个轴突投射出现在尾侧 大细胞基底核（cMBN）并终止于丘脑内 网状核（TRN）。该通路的终末终扣为 发现经常突触上的胞体和近端树突的TRN 神经元，具有对称的膜特化。虽然我们有，由 在将WGA-HRP点状注射到神经元中后检查标记的神经元。 TRN，确定了cMBN内的一些神经元， 标记和阳性的GABA，重要的是要确认GABA能 在cMBN本身内产生的轴突的处置使用顺行性 示踪剂，因为通道纤维对示踪剂的摄取是一个问题。 使用PHA-L结合MM免疫组织化学，我们发现许多， 尽管并非所有在CMBN中产生的TRN内的终扣都包含GAD。 总的来说，这些发现表明，外源性GABA能输入 进入TRN，并证明一个这样的输入明确出现 在CMBN中。 使用多巴胺-β-羟化酶（DBH）免疫组织化学，我们有 接着检查TRN和TRN上的去甲肾上腺素能（NA）输入， cMBN。胸径~+钮子密度最高的部位是TRN，而胸径~+钮子密度最高的部位是TRN 轴突终扣均匀分散，并专门产生终扣， 过路人与此相反，cMBN内的DBH+轴突被视为合并 偶尔出现的簇状病灶似乎与某些神经元相邻， 尽管许多DBH+轴突也产生分散的终扣。 通过结合DBH免疫组织化学和细胞内注射 荧光染料，荧光黄（LY）进入TRN神经元。我们研究了 NA轴突与TRN神经元的关系。DBH+ bouton 所有直径的树突都发生了增大， 随机地接触它们碰巧相交的树突。 在将固蓝（FB）注射到TRN中之后，逆行标记的cMBN 神经元也注射LY。虽然表面上的随机接触 DBH+注射cMBN神经元的具有树突状轮廓的轴突终扣， 偶尔发现，焦点集群没有发生在有关 投射到TRN的cMBN神经元的子集。PHA-L注射到 蓝斑（LC）揭示了两个群体的DBH+轴突（在 TRN和cMBN）在LC内出现，并且逆行双标记 实验表明，在LC内，投射到 这两个地点在很大程度上是相互独立的。 因此，上升网状激活系统，长期以来一直保持上升 只在脑干网状结构内的某个地方，也可能是 基本上受端脑的影响（通过cMBN）。一个上升 脑干系统，NA系统，可能强烈和直接影响 TRN，但似乎并不准备对 由cMBN->TRN途径传递的信号。

We had previously identified an axonal projection arising in the caudal magnocellular basal nucleus (cMBN) and terminating within the thalamic reticular nucleus (TRN) in rats. The terminal boutons of this pathway were found to frequently synapse upon both somata and proximal dendrites of TRN neurons, with symmetric membrane specializations. Although we had, by examining labeled neurons following punctate WGA-HRP injections into the TRN, identified some neurons within the cMBN that are both retrogradely labeled and positive for GABA, it was important to confirm the GABAergic disposition of the axons arising within the cMBN itself using anterograde tracers, since the uptake of tracers by fibers of passage was a concern. Using PHA-L in conjunction with MM immunohistochemistry, we find that many, though not all boutons within the TRN arising in the CMBN contain GAD. Collectively these findings indicate that an extrinsic GABAergic input enters into the TRN, and demonstrate that one such input clearly arises within the CMBN. Using dopamine-beta-hydroxylase (DBH) immunohistochemistry, we have proceeded to examine the noradrenergic (NA) input upon the TRN and the cMBN. The highest density of DBH+ boutons occurs in the TRN; the DBH+ axonal boutons are evenly dispersed and give rise exclusively to boutons en passant. In contrast, the DBH+ axons within the cMBN are seen to coalesce into occasional clustered foci which appear to abut upon certain neurons, although many DBH+ axonsals also give rise to dispersed boutons en passant. By combining DBH immunohistochemistry with intracellular injections of the fluorescent dye, Lucifer yellow (LY) into TRN neurons. we examined the relationship of NA axons to the neurons of the TRN. The DBH+ bouton enlargements occurred in relation to dendrites of all diameters, appearing to randomly contact whichever dendrites they happened to intersect. Following fast blue (FB) injections into the TRN, retrogradely labeled cMBN neurons were also injected with LY. Although apparent random contacts of DBH+ axonal boutons with dendritic profiles of injected cMBN neurons were occasionally identified, the focal clusters did not occur in relation to the subset of cMBN neurons which project to the TRN. PHA-L injections into the locus coeruleus (LC) reveal that both populations of DBH+ axons (in the TRN and in the cMBN) arise within the LC, and retrograde double labeling experiments indicate that within the LC, the cell populations projecting to these two sites are largely independent of one another. Thus, the ascending reticular activating system, long held to arise exclusively somewhere within the brainstem reticular formation, may also be substantially influenced by the telencephalon (via the cMBN). One ascending brainstem system, the NA system, may strongly and directly influence the TRN, but does not appear to be poised to have a significant influence upon the signals conveyed by the cMBN-->TRN pathway.